(1) Field of the Invention
The present invention relates to ceramic member-electric power supply connector coupling structure.
(2) Description of Related Art
Nowadays, electrostatic chucks are being used to adsorb and hold semiconductor wafers in transferring, light-exposing, film-forming such as CVD and sputtering, fine processing, washing, etching, dicing, etc. for semiconductor wafers. Dense ceramics are noted for substrates of such electrostatic chucks. Particularly in the semiconductor producing apparatus, a halogen based corrosive gas such as ClF.sub.3 is often used as an etching gas or a cleaning gas. In order to rapidly heat and cool the semiconductor wafer while being held by such a substrate, the substrate of the electrostatic chuck is desired to have high heat conductivity. Further, it is desired that the substrate have such heat shock resistance so as not to be destroyed by rapid temperature changes. Dense alumina nitride and alumina have high corrosion resistance against the halogen based corrosion gas mentioned above.
In the field of the semiconductor producing apparatuses, susceptors in with built-in high frequency electrodes for generating plasma have been practically used. In the field of such high frequency electric power generating apparatuses, a metal electrode is buried in a substrate of aluminum nitride or dense alumina. Further, in the field of the semiconductor producing apparatuses, ceramic heaters in which a metallic resistor is buried in a substrate of aluminum nitride or alumina for controlling the temperature of a wafer in each process.
In these apparatuses, it is necessary that the metal electrode be buried in the ceramic substrate made of aluminum nitride or the like, and that the metal electrode be electrically coupled to an external electric power supply connector. However, a coupling portion for this purpose is exposed to a heat cycle between extreme high temperatures and low temperatures in an oxidative atmosphere and further in a corrosive gas atmosphere. Such a joining portion is desired to maintain high joining strength and excellent electric coupling performance for a long time period even under such a bad condition.
The present inventors have continuously studied the coupling structures as mentioned above. For example, a Japanese patent application No. 8-24,835 disclosed that the tip of an electric power supply connector was coupled to a metal electrode in a susceptor with an Al alloy brazing material, a Cu alloy brazing material or a Ni alloy brazing material having high corrosion resistance. Further, JP8-24,836 proposed that a mesh or net metal electrode be buried in an AlN ceramic, while a part of the mesh or net metal electrode be exposed, and the exposed mesh or net portion and the AlN ceramic be both brazed to a tip face of the electric power supply connector.
Although these Japanese patent applications proposed the brazing methods which would ensure high corrosion resistance against the halogen based corrosive gas and the plasma, a specific coupling structure which would maintain high joining strength and excellent conductivity even under exposure to high temperatures and heat cycle in the oxidative atmosphere has not been investigated in detail with respect to the coupling structure for the connector and the metallic electrode.